Aim:

Controlling the retraction and extension of Airplane’s landing gear can be implemented using Finite State Machine (FSM). FSM is the most efficient algorithm which is mathematical model of computation.

Key Highlights of the Project:

A direction valve is controlled by the software to allow the hydraulic pressure to either raise or lower the landing gear.

Deliverables of this project:

Implementing the control for the retraction and extension of Airplane’s landing gear using the Finite state machine with the knowledge of various states of switch and gear.

Expected Outcomes:

Knowledge of Finite State Machine algorithm which is used to achieve the control over the retraction and extension of Airplane’s landing gear using the switch and gear states of Airplane.

Finite State Machine:

A finite-state machine (FSM) or finite-state automaton (FSA, plural: automata), finite automaton, or simply a state machine, is a mathematical model of computation. It is an abstract machine that can be in exactly one of a finite number of states at any given time. The FSM can change from one state to another in response to some inputs; the change from one state to another is called a transition.

Implementation of the Project:

Finite State Machine of Airplane's landing gear:

Code:

#include <stdio.h> //creating seven function we want to carry out the process or controlling sets of gear under different condition.Based on FSM.
void Initiate_State_Machine();
void GearDown();
void CheckingBeforeTakeOFF();
void RaisingGear();
void GearUp();
void CheckBeforeLanding();
void LoweringGear();
static void(*statetable[])(void)={GearDown, CheckingBeforeTakeOFF, RaisingGear, GearUp, CheckBeforeLanding, LoweringGear}; //array of 6 element to access the finction based on require ment.In the name of static table.
typedef enum State // creating four type of enum in program
{
GEAR_DOWN,
CHECKING_BEFORE_TAKEOFF,
RAISING_GEAR,
GEAR_UP,
CHECK_BEFORE_LANDING,
LOWERING_GEAR,
}State_Type;
typedef enum Switch
{
on,
off
}Switch_status;
typedef enum pilot_lever
{
Raising,
falling
}pilot_lever;
typedef enum hydraulic_mechanism
{
working,
not_working
}hydraulic_mechanism;

static volatile Switch_status squat_switch; // creating the object name for the 4 enum structures
static volatile Switch_status limit_switch;
static volatile pilot_lever pl;
static volatile hydraulic_mechanism hm;

State_Type current_state;

typedef struct // creating the structure where giving the different condition where how to control the landing gears.
{
char* current_state_indication;
char* light;
char* direction_valve_status;
char* landing_gear_hydraulic_control;
char* Gas_Pressurized_Spring_system_status[2];

}State_Table;

static State_Table State_Machine[6]={{"GearDown","Green","Down","Enabled",{NULL,NULL}},
{"CheckingBeforeTakeOFF","Green","Down","Enabled",{NULL,NULL}},
{"RaisingGear","Red","Up","Enabled",{NULL,NULL}},
{"GearUp","Off","NULL","Disbled",{NULL,NULL}},
{"CheckBeforeLanding","Red","Down","Enabled",{NULL,NULL}},
{"LoweringGear","Green","Down","Enabled",{"Disabled","Enabled"}}
};
int main() // creating the main function
{
Initiate_State_Machine();
while(1)
{
statetable[current_state]();
}
}
void GearDown(void) // in main function we are calling the function name is Intiate State machine function
{
current_state=GEAR_DOWN;
printf("Enter the status of pilot's lever and squat switch");
fflush(stdout);
scanf("%d %d",&pl,&squat_switch);
if(pl==Raising && squat_switch==on)
{
current_state=CHECKING_BEFORE_TAKEOFF;
printf("current state:%s\n",State_Machine[current_state].current_state_indication);
printf("Light is :%s\n", State_Machine[current_state].light);
}
else
{
GearDown();
}
}

//CheckingBeforeTakeOFF
void CheckingBeforeTakeOFF(void)
{
current_state=CHECKING_BEFORE_TAKEOFF;
printf("Enter the status of pilot's lever and squat switch and hydraulic mechanism:");
fflush(stdout);
scanf("%d %d",&pl,&squat_switch,&hm);
if(pl==falling&&squat_switch==off)
{
GearDown();
}
else if(pl==Raising && squat_switch==on && hm==working)
{
current_state=RAISING_GEAR;
printf("Current State:%s\n",State_Machine[current_state].current_state_indication);
printf("Light is:%s\n",State_Machine[current_state].light);
printf("Status of Direction valve:%s\n",State_Machine[current_state].direction_valve_status);
}
else if(pl==Raising && squat_switch==on && hm==not_working)
{
current_state=RAISING_GEAR;
printf("Current State:%s\n",State_Machine[current_state].current_state_indication);
printf("Light is:%s\n",State_Machine[current_state].light);
printf("Status of Direction valve:%s\n",State_Machine[current_state].direction_valve_status);
printf("Status of gas pressurised Spring System:%s\n",State_Machine[current_state].Gas_Pressurized_Spring_system_status);
}
}
//RaisingGear
void RaisingGear(void)
{
current_state=RAISING_GEAR;
printf("Enter the status of pilot's lever and limit switch:");
fflush(stdout);
scanf("%d %d",&pl,&limit_switch);
if(pl==falling && limit_switch==on)
{
current_state=CHECK_BEFORE_LANDING;
printf("Current State:%s\n",State_Machine[current_state].current_state_indication);
printf("Light is:%s\n",State_Machine[current_state].light);
printf("Landing Gear Hydraulic Control:%s\n",State_Machine[current_state].landing_gear_hydraulic_control);
}
else if(pl==Raising && limit_switch==off)
{
current_state=GEAR_UP;
printf("Current State:%s\n",State_Machine[current_state].current_state_indication);
printf("Light is:%s\n",State_Machine[current_state].light);
printf("Landing Gear Hydraulic Control:%s\n",State_Machine[current_state].landing_gear_hydraulic_control);
}
else
{
RaisingGear();
}
}
//GearUp
void GearUp(void)
{
current_state=GEAR_UP;
printf("Enter the status of pilot's lever:");
fflush(stdout);
scanf("%d",&pl);
if(pl==falling)
{
current_state=CHECK_BEFORE_LANDING;
printf("Current State:%s\n",State_Machine[current_state].current_state_indication);
printf("Light is:%s\n",State_Machine[current_state].light);
printf("Landing Gear Hydraulic Control:%s\n",State_Machine[current_state].landing_gear_hydraulic_control);
}
else
{
GearUp();
}

}
//CheckBeforeLanding
void CheckBeforeLanding(void)
{
current_state=CHECK_BEFORE_LANDING;
printf("Enter the status of pilot's lever and hydraulic mechanism status:");
fflush(stdout);
scanf("%d %d",&pl,&hm);
if(pl==falling && hm==working)
{
current_state=LOWERING_GEAR;
printf("Current State:%s\n",State_Machine[current_state].current_state_indication);
printf("Light is:%s\n",State_Machine[current_state].light);
printf("Status of Direction valve:%s\n",State_Machine[current_state].direction_valve_status);
}
else if(pl==falling && hm==not_working)
{
current_state=LOWERING_GEAR;
printf("Current State:%s\n",State_Machine[current_state].current_state_indication);
printf("Light is:%s\n",State_Machine[current_state].light);
printf("Status of Direction valve:%s\n",State_Machine[current_state].direction_valve_status);
printf("Status of gas pressurised Spring System:%s\n",State_Machine[current_state].Gas_Pressurized_Spring_system_status);
}
else if(pl==(Raising))
{
CheckBeforeLanding();
}
}
//LoweringGear.
void LoweringGear(void)
{
current_state=LOWERING_GEAR;
printf("Enter the status of pilot's lever and limit switch:");
fflush(stdout);
scanf("%d %d",&pl,&limit_switch);
if(pl==falling && limit_switch==on)
{
current_state=CHECKING_BEFORE_TAKEOFF;
printf("Current State:%s\n",State_Machine[current_state].current_state_indication);
printf("Light is:%s\n",State_Machine[current_state].light);
}
else if(pl==Raising && limit_switch==off)
{
current_state=GEAR_DOWN;
printf("Current State:%s\n",State_Machine[current_state].current_state_indication);
printf("Light is:%s\n",State_Machine[current_state].light);
printf("Landing Gear Hydraulic Control:%s\n",State_Machine[current_state].landing_gear_hydraulic_control);
}
if(limit_switch==off)
{
LoweringGear();
}
}
//Initiate_State_Machine
void Initiate_State_Machine()
{
current_state==GEAR_DOWN;
printf("The Finite State Machine is Intialized and current the program is in""GearDown State & Light is:%s\n",State_Machine[current_state].light);
}

Output:

The Finite State Machine is Intialized and current the program is inGearDown State & Light is:Green
Enter the status of pilot's lever and squat switch0 0
current state:CheckingBeforeTakeOFF
Light is :Green
Enter the status of pilot's lever and squat switch and hydraulic mechanism:0 0
Current State:RaisingGear
Light is:Red
Status of Direction valve:Up
Enter the status of pilot's lever and limit switch:0 0
Enter the status of pilot's lever and limit switch:0 1
Current State:GearUp
Light is:Off
Landing Gear Hydraulic Control:Disbled
Enter the status of pilot's lever:0 0
Enter the status of pilot's lever:Enter the status of pilot's lever:1 0
Current State:CheckBeforeLanding
Light is:Red
Landing Gear Hydraulic Control:Enabled
Enter the status of pilot's lever and hydraulic mechanism status:1 1
Enter the status of pilot's lever and hydraulic mechanism status:1 0
Current State:LoweringGear
Light is:Green
Status of Direction valve:Down
Status of gas pressurised Spring System:��)��U
Enter the status of pilot's lever and limit switch:0 0
Enter the status of pilot's lever and limit switch:1 0
Current State:GearDown
Light is:Green
Landing Gear Hydraulic Control:Enabled